It’s a common doubt that why the mobile SIM cards have a unique cut shape??. Before going to answer this question let’s discuss some basics of SIM card.
Subscriber’s identity Module (SIM) card is a removable electronic chip which is used to identify the subscriber in a mobile telephonic network. SIM card is basically an electronic chip with an embedded micro controller with a memory. Sim cards having eight contacts embedded on the card. The SIM card used in mobile phone has a width of 25 mm, a length of 15 mm, and a thickness of 0.76 mm.
International Organization for Standardization(ISO) and International Electrotechnical Commission are the agencies standardize the SIM cards. The cards are standardized as per ISO 7816-1 describes the physical characteristics of cards and ISO 7816 part 2 defines the dimensions and location of the contacts(for details- visit).
Let’s comeback to our topic. The main reason for the cut mark on the corner is to avoid the misalignment of the contacts of SIM card and mobile phone cardholder pins. Pin number 1 of the SIM card to make the contact with the corresponding pin of the mobile phone. The cut mark serve as a guide for proper placement of card in mobile phones. As it is internationally accepted by ISO, being followed by all the mobile phone manufactures.